Regarding the weird fins, as we all know the further away from our feet the rear fin is, the less a board will yaw. If I had put a fin box in, this distance would have been reduced 12" or so, the black ugly thing swept as far back as possible just maximises the resistance to yaw, so with every paddle stroke a little more forward direction is produced, instead of snaking down the river.
The sweep is for two reasons, obviously the point I have just mentioned, & weed, there can be a fair bit in the river at times.
The forward fin is made for the same reasons, not to catch weed & as forwadrd as possible to maximise effect.
The result is a board that is a pleasure to paddle, greatly reducing the board yawing away along the intended track.
To turn the boards, the method is no different to any board, a sweep stroke here & there to guide along a course, or to round a buoy, step back, nose out & a few sweeps...off you go in the opposite direction. (or you can cheat....leave the board flat on the water, turn yourself on the board & take off the other way bacwards

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I would even suggest the 14' nash downwinder if paddled bacwards with a fin taped near the nose, & the tail fin left were it is, would go faster on FLAT WATER. Rather than pushing that huge nose lift through the water & yawing along.
Could you imagine a bush mechanic doin that at the recent canal race in Germany....& doing well

Hey DJ, I have a spare fin & duct tape we can do a "myth busters"